Air interlock control for gas burning apparatus



Dec. 8, 1959 P. ARANT 2,916,022

AIR INTERLOCK CONTROL FOR GAS BURNING APPARATUS Filed April 17, 1951 2Sheets-Sheet 1 INVENTOR penyAz mfi.

37 you, J/Kmmm/ ATTORNEYS P. ARANT 2,916,022

AIR INTERLOCK CONTROL FOR GAS BURNING APPARATUS Dec. 8, 1959 Filed April17. 1951 2 Sheets-Sheet INVENTOR United States Patent AIR INTERLOCKCONTROL FOR GAS BURNING.

APPARATUS Perry Arant, San Gabriel, Calif., assignor to ClaytonManufacturing Company, El Monte, Calif, a corpora -tion of CaliforniaApplication April 17, 1951, Serial No. 221,417

4 Claims. (Cl. 122-504) The present invention relates to automaticburner control apparatus and more particularly to control apparatus foruse with forced draft gas-burning equipment, such as gas-burning steamcleaners, steam generators, space heaters, and the like.

More specifically, the invention relates to air interlock means forcontrolling the operation of the main gas valve, and which means willprevent opening of the main gas valve and the flow of gas to the burner,unless the blower providing the forced draft is in operation.

The control means comprising the present invention is particularlyadapted for use as a further safety device in conjunction with knownsafety controls, such as stack switches, pressure switches, thermostats,thermo couplings, automatic ignition and spark control devices,electronic flame rod rectifiers, etc., .which provide for shut ting downof the apparatus, or ignition proving before restarting, but do notafford pnotection against the possible flow of gas to the burner whenthe apparatus is standing by or not in operation at all. Experience hasshown that a number of combustion chamber explosions have occurred, evenwith machines equipped with ignition failure checking devices, due tothe lack of adequate gas flow control means effective during an offperiod, thus making it possible for the combustion chamber to becomefilled with explosive gas before the unit is restarted.

The principal object of the invention is to provide auxiliary safetycontrol means which will positively pre vent the flow of gas to theburner of gas-fired apparatus, unless the blower furnishing air forforced draft is in operation.

Another object of the invention is to provide auxiliary control meansfor a gas burner which will automatically shut off the flow of gas tothe burner whenever the apparatus is shut down, either manually orautomatically.

Another object of the invention is to provide a safety control for gasburning equipment employing forced draft, which includes air interlockmeans associated with the blower and main gas valve for preventing theflow of all gas to the burner in the event that the air pressuredeveloped by the blower is below a given minimum.

Another object of the invention is to provide a main gas supply valvewhich will automatically close and prevent gas flow to the burner in theevent of excessive t ss rs l rr n n th a upp y l Another object of theinvention is to provide an airpressure operated (diaphragm) main valvefor gas-burning equipment .wherein gas flow to the combustion chamher isshut off in event of diaphragm failure.

Still another object bf the invention is to provide a safety controlforgas burning equipment which is independent of, although adapted for usein conjunction with, the usual safety {controls including those employedfor ignition pr oving. and which latter do not afford protectionagainstthe flow of gas to the burner during an gas to the pilot tube'18.

shut-off cock 22 is connected in the conduit 20 at a point 2,916,022fatentecl Dec. 8, 1959 Still another object of the invention is toprovide a gas supply control valve which will not open except inresponse to the operation of means actuated by air pressure created byoperation of the blower.

Other objects and advantages of the invention will be apparent from thefollowing description taken in conjunction with the accompanyingdrawings, in which:

Fig. 1 diagrammatically illustrates a preferred form of burner controlsystem for a gas-fired steam generator embodying the principles of thepresent invention;

Fig. 2 is a vertical sectional viewtaken through the air-pressureoperated main gas control valve shown in Fig. 1; and

Fig. 3 is a vertical sectional view through a normally open,spring-loaded air control valve, adapted to be closed by a thermallyexpansible element, also shown in Fig. 1.

"Referring now to Fig. 1 of the drawings, the reference numeral 1generally identifies a steam generating apparatus including a housing 2containing a heating coil 3 having an inlet end 3 and a discharge end3'. The discharge end 3 of the heating coil 3 is connected to astationary housing 4 by a pipe 4*. A tube 4 has one end thereof securedto the housing 4 and constitutes a continuation of the pipe 4*. Athermally responsive element 4 surrounds the tube 4' and has one endthereof communicating with a chamber 4 in the housing 4 and its otherend 4 is closed but free to move for a purpose explained later.Adischarge pipe 4 communicates at one end with the chamber 4 and itsother end is connected to a conventional steam separator 5. A conduit -5conducts the steam from the separator 5 to the point of use. Thethermally responsive element 4 extends across a combustion chamber 6having a gas burner 7 projecting upwardly into the lower end thereof.The burner 7 includes a tubular portion 8 which is connected by an elbow9 to one end of a 'gas supply pipe 10, the opposite end of said pipebeing connected with a main gas supply control valve l'lfwhich will bedescribed in detail later. A manually operable main gas cook 12 isconnected in the gas pipe 10 ahead of the valve 11. The valve 11 isdesigned to control the flow of gas at a feed pressure equal to :a 3"'to 10 water column. An air supply chamber 13 surrounds the tube '8 ofthe burner 7 and is disposed below the combustion chamber '6. Forceddraft or air under pressure is supplied to the chamber 13 through a duct14 by a conventional volute blower 15. Air fromthe chamber 13 passesthrough an opening 16 in the housing 2 andthrough a sleeve 17 disposedabove the opening 16 into the combustion chamber 6 for admixture withthe gas supplied to the burner 7 for effecting complete combustion ofthe gas'and'heating of the water in the coil 3.

The burner 7 includes a pilot tube 18, arranged concentrically in thetube portion 8, and having its upper end extending into the combustionchamber 6 and having its lower end connected with one side of a 3-wayboss 19 formed integral with the elbow 9. The opposite side 'of the boss19 is connected to one end of a conduit '20, the other end of which isconnected with the inlet side of the main gas cock 12. A conventionalsolenoid valve 21 is connected in the conduit 20 for controlling theflow of A manually operable pilot that air is mixed with the pilot gassupplied to they pilot tube 18 before it reaches the combustionchamber6.

The main gas supply control valve 11 is illustrated in detail in Fig. 2to which'reference will now be made. ,1

This valve comprises a body portion 24 having an inlet chamber 25 and anoutlet chamber 26 separated by a partition 27. A portion of the gas pipeis received in a threaded opening 28 on. the inlet side of the valve 11,and another portion of; said pipe is received in a threaded opening'29on the outlet side of said valve. Thepartition 27fhas a threaded opening30 in which a threaded annulaf member 31 is mounted. The upper surfaceof the member 31 is beveled to provide a seat 32 engaged by a rubbersealing member 33 carried by a valve disc 34. The sealing member 33 iscentrally apertured to receive a cylindrical sleeve 35 engaged at itsopposite ends by Washers 36 and 37. A valve stem 38 is engaged at itsupper end with the washer 37, and a valve stemextension 39 hasahexagonal portion 40 intermediate its ends 'engaged 'with the washer 36and a part that extends through the washer 36, sleeve 35 and washer 37into a threaded opening 41 formed in the upperendof the valve stern 38,and thus serves to fixedly secure the valve ,;disc 34 to the valve stem38.;- f z The valve body 24 has an opening 42 formed therein A above thevalve disc 34, thisopening'is closed by a cover plate 43 secured to saidbody portion by a plurality of cap-screws 44. 'A"centrally locatedhollow projection 45 is formed on the cover 43 and is adapted to receivethe upper end of the valve stem extension 39. Ailug' .46 extendsdownwardly from the inner face of the cover 43 and serves as a supportfor one forked end' of ailever 47, said lever 'being pivotally connectedto the lug 46 by a pin 48.' The opposite or free end of the lever 47 isalso forked and portions thereof extend'around the valve stem extension39 and engage with a convex surface 49 formed above the hexagonalportion 40 of said valve stem extension. A roller 50 is mounted upon thelever 47 adjacentthe lug 46 by a pin 51. The free end of. the lever 47rests upon the convex surface 49 and normally tends to urge the sealingmember 33 intoengagement with the seat 32 by gravity to prevent the flowof gas through the valve. .1

The cover member 43 is provided with an opening 52 disposed directlyabove the roller 50 forthe reception of the lower end of a rod 53., Therod 53 is grooved and carries a sealing O-ring 54 for preventing theescape ofi'g'as from the inlet chamber 2 5 to the atmosphere. The stem53 forms a part of a conventional steam pressure responsive actuator'55,which includes a housing 5 6- having its base secured to the covermember 43 by cap screws 57. a A piston 58 is mounted upon the upper endof the rod 53 and its top surface is engaged by a flexible diaphragm59.1 A cover 60 is disposed above the diaphragm 59 and is secured to thehousing 56 by a plurality of screws 61. The cover 60 is hollowed out toprovide a pressure chamber 62 vabove the diaphragm 59.

A threaded opening .63 is disposed below the diaphragm I i 59, and anexternally threaded cylindrical sleeve' 64 is adjustably mounted in saidopening. A compression sprlng 65 is arranged in surrounding relationwith the rod 53 between the piston 58 and the lower end of the sleeve64, so that the pressure required in the chamber 62 to effect downwardmovement of the rod 53 can be varied asdesired. i I i One end of aconduit 66 is connected to the cover 60 1 in the air'tube 89'at apointbetween the main gas 'valve in communicating relation with the chamber62, and'its other end is connected to the steam separator 5 (Fig. 1)

. so that the pressure in said steam separatoris communicated to saidchamber and acts downwardly upon the diaphragm 59 tending tcT'efiectdownward movement of the-rod;53 against the resistance offered by spring65. Thusgshould the steam press'urein the separator 5 exceedthe pressureforwhich the spring has been set, the ro d;53 will be, moved downwardlyinto engagement wth 'theiroller 50 carried by" the lever 47 to force thevalve stem ,38 dow'nwardly and thereby cause the sealing member-33ndengagewith the.seat'32 to positively close .7 the :valve 11" and cut011. all-"communication between the inlet chamber .25 and theioutletchamber 26. This action,

'11 against the gas line pressure of 6" to 8" water column. J

of course, will cut ofi? the supply of fuel to the burner 7 and providesa safety means to prevent the building up of excess steam pressure inthe steam separator 5.

The valve body 24 has a bottom wall provided with 'an opening 67vertically aligned with the threaded opening 30. A flexible gas sealdiaphragm 68 extends acrosstlie opening 67 and is secured at its outermargin to said bot tom wall by a ring 69 and a plurality of screws 70.Washers 71 and 72 are disposed upon opposite sides of the diaphragm 68with the washer 71 engaging the lower endof the valve .stem 38, whichhas an aperture provided with threads '73. A spacer member 74 has ashoulder adapted to engage with the washer 72 and a threaded extension75, which extends through the washer 72, diaphragm 68 and washer71 intoengagement with the threads 73. Thus, the diaphragm 68 is firmly securedto the lower end of the valve sten138. i

'A dished member or pan 76 has an outwardly extending flange 77 disposedbelow' a cooperating flange 78 depending from the valve body 24 insurrounding relation to the diaphragm 68. A flexible air and gasimpervious diaphragm 79, of a diameter substantially larger than thediaphragm 68, is disposed between the flanges 77 and 78, and cap screws80 secure said diaphragm .and the. dished member 76 to the valve body24. Thus, an inter-. mediate chamber 77 is formed bythe valve body 24,the flange 78, and the diaphragms 68 and 79. The flange 78 has a ventopening 78 extending ther'ethrough for venting the chamber 77% to theatmosphere to provide for free relative movement of the diaphragms 68and 79. A diaphragm supporting plate 81 is disposed. in the intermediate chamber 77 and is engaged with the upper side, of the airdiaphragm 79 and provides a support for substantially the entire area ofsaid diaphragm. The plate 81 is secured to the head of the spacer 74-bya screw 82 extending centrally through said plate and into a threadedopening in said spacer. The pen 76 hasan outwardly and upwardly inclinedside wall 83 which merges into the flange 77. vThe sidewall 83 isprovided with a threaded opening 84 in which a plug 85 is mounted; Theplug 85 has a vent orifice o1 bleed opening 86 formed therein whichserves as a bleeder for continuously estate lishing communicationbetween a pressure chamber87, jointly defined by the dished member 76and the diaphragm 79, and the atmosphere. A boss 88 projects outwardlyfrom the sidewall 83 and has one end of a section 89 of an air tube 89connected thereto, the" 1 Valve 91, l, which will be described in detaillater.-

The inlet of the air valve '91 has one'end of another air tube sectionv89 connected'thereto and its opposite end is connected with the airduct 14 'at a point indicated the numeral '92. Thus, the solenoid'valve'90 is connected 11 and the air valve 91. In the case of a 100 hp. steamgenerating unit, the main gas valve 11 maybe a 3" valve, in which eventthe bleeder hole 86 would be 0,177 in diameter to maintain a static airpressure equal'toabo'ut a 3" water column on' the diaphragm 79 when theblower 15 is in operation; such pressure acting on the large area of thediaphragm 79 being adequate 'to open the valve The air valve 91 is showncross-sectional detail in Fig. 3 and comprises a generallycup-shapedbody 94 and a'cover 95-forming a "closure for the open end of saidbodyfsaid cover beingisecuredto" said body by a plurality of capscrews96g A boss'97 projects inwardly from the bo'ttomwall of the body94and forms a guide "for a valve stem'98. The valve stem 98 isconventionally grooved to receive split'contractile' snap rings'99 and100; 7 5

A disc; 191 is disposed adjacent to snap ring 100 and a compressionspring 102 is disposed between the disc 101 and the snap ring 99,whereby the disc 101 is mounted for axial movement on the stem 98 topermit over-travel of the stem 98 toward the right. A compression spring103 is disposed in the cover 95 on the opposite side of the ring 100 andtends to maintain the disc 101 spaced away from a seat 104 formed on thecover 95. In other words, the spring 103 tends to maintain the air valve91 open at all times. The stem 98 projects to a point exteriorly of thevalve body 94 and is adapted to be engaged by the end '4 of thethermally responsive tube element 4, which is subject to the heat of thegases in the combustion chamber as well as the heat of the liquid beingheated in the coil 3, inasmuch as liquid discharged from the tube 4 mustreverse its direction of flow infthe tube 4 before it can flow into thedischarge pipe 4 The arrangement is such that, should there be a failureof the water supply, the thermally responsive element 4 will expand orelongate and urge the stem 98 toward the right, as viewed in Fig. 3, toeffect engagement of the disc 101 with its seat 104 to prevent the flowof air under pressure through the valve 91. Of course, as the air valve91 closes, the pressure communicated to the chamber 87 of the gas valve11 will drop, thereby permitting the main gas valve to closeautomatically and cut off the supply of gas to the burner and preventbuming out of the heating coil. The same result can be effected by theclosing of the solenoid valve 90, which will likewise function to shutoff the flow of air to the pressure chamber 87, as explainedhereinafter.

A conventional electronic flame scanner control device 105 may becombined with the present air operated main gas valve 11 to control themain solenoid valve 90 through conductors 106 and 107, but this is notessential for the reason that the solenoid valve 90 could be controlledby any other conventional means. Likewise, the pilot solenoid valve 21may be connected through conductors 108 and 109 with the electroniccontrol device 105. shich electronic control devices utilize theprinciple of flame rectification or flame conduction, and are well knownto those familiar with the art. Hence, there is no need for illustratingor describing such devices in detail herein. However either type ofconventional control includes an electrode 110 placed adjacent theburner 7 and adapted to ignite the gas pilot 18. The electrode 110 isconnected with the electronic control device 105 by a conductor 110',which supplies current of high potential thereto, and arcs to ground onthe pilot housing. Another electrode 111, more commonly called a flamescanner rod, is connected to the electronic control device 105 by aconductor 111'.

When the unit is started by manual operation of a push button on thecontrol device 105, or by automatic pressure switch control (not shown),current to the electrode 110 and pilot solenoid valve 21 aresimultaneously supplied, so that gas is supplied to and the pilot 18 isignited. The flame scanner electrode 111 is positioned for contact bythe pilot flame and heating thereof causes electric currentrectification or conduction and actuates, through the electronic controldevice 105 and conductors 106 and 107, the solenoid valve 90 in the airline 89 to effect opening of the main gas valve 11. In the event thatthe pilot 18 is unstable or flame rectification or conduction with thescanner rod 111 is not consistent, the electronic control device 105will revert back to starting condition, closing the valve 90 andreestablishing ignition through the electrode 110 at the gas pilot 18.If the unit is running at any time without proper flame rectification orconduction (depending upon which type of automatic electronic controldevice 105 is employed), the power source (electric current), whichnormally flows through a warp switch (not shown), is interrupted byopening of said switch and the unit is stopped after a period of aboutone minute.

For present purposes, it will be assumed that the gas 6 pilot 18 is lit,and that the conventional electronic control 105 has energized the aircontrol solenoid valve to maintain the same in open position. Air underpressure is then diverted from the casing 14 through the air tubesection 89 to the inlet of the air valve 91, which valve is normallymaintained open by the spring 103, as above pointed out, so that the airunder pressure is further conducted through the tube section 89 and theopen solenoid valve 90 and thence through the tube section 89 to thepressure chamber 87 in the main gas valve 11. The air under pressurewill act upon the diaphragm 79 and flex it upwardly, thereby raising thevalve stem 38 and lifting the sealing member 33 out of engagement withthe seat 32 to permit gas to flow through the pipe 10 to the burner 7.The air bleed opening 86 will, of course, permit air under pressure tocontinuously escape from the chamber 87 to the atmosphere at arestricted rate. Normally, a pressure equivalent to only 3" of water isrequired to effect opening of the gas valve 11, and the blower 15 isadequate to supply such low pressure at all times. The valve 11 willnormally remain open so long as fuel is required to heat the liquidpassing through the coil 3. Should the steam demand on the steamgenerating unit 1 drop to the point where an excess of steam pressuredevelops in the steam separator 5, such steam pressure will be effectivethrough the conduit 66 to act upon diaphragm 59 causing the rod 53 tomove downwardly into engagement with the roller 50 and actuate the lever47 to move the valve stem 38 downwardlyand thus positively shut off theflow of gas through the valve 11. On the other hand, an independentcontrol of the supply of gas to the burner is possible through theclosing of the air valve 91 by the thermal expansion of the element 4,the latter acting on the stem 98 to engage the disc 101 with its seat104. Any excess expansion of the element 4 cannot damage the valve 91because of the loose mounting of thedisc 101 on the stem 98 compensatingfor any valve stem over-travel. When the valve 91 is closed, the supplyof air under pressure to the chamber 87 is cut off and pressure in saidchamber is immediately reduced by the bleeding of the air from thechamber through the bleeder hole 86 until the pressure in the chamber 87is reduced to atmos pheric, thus permitting the valve 11 to closeautomatically.

A further and independent control of the gas valve 11 is providedthrough the solenoid valve 90 controlled by the conventional electronicflame scanning apparatus 105 which would de-energize the solenoid valve90 and permit it to close in the event of flame failure. Hence, if theburner flame should go out for any reason, the solenoid valve 90 wouldbe automatically closed, cutting off the supplyof air under pressure tothe chamber 87! even though the blower 15 continues to operate, wherebyclosing of the valve 11 will be quickly effected through the bleeding ofair under pressure to the atmosphere through the orifice 86, aspreviously explained. Moreover, in the event of failure of the blower15, or manual hut ti w sf the a a at there w uld be o a n e pressuredelivered to the chamber 87 and the valve 11 would automatically closeto shut off the supply of gas to the burner 7.

It will be clear from the foregoing that the present apparatus providesan air interlock control for the main gas valve 11, which is independentof the usual and conventional controls, and which will prevent all gasfrom flowing to the combustion chamber 6 unless an adequate supply ofair is being furnished to the combustion chamber.

It will be understood that, in the event that the pressure in the gasline connected to the inlet of the valve 11 should rise to about 12"water column pressure, such pressure would overcome the 3" water columnpressure of the air in the chamber 87 acting on the diaphragm 79 tendingto maintain the valve 11 open, with the result that the valve 11 will beclosed, thereby automatically preventing the delivery of'gas atexcessive pressure to the burner 7. This feature also constitutes avaluable safety control for the apparatus. T; i

It will also be understood that in the event of any diaphragm failure,the valve 11 will close similar to a check valve due to the intermediateatmospheric chamber 77 and the direction of normal gas flow through thevalve, allowing a safe failure. 1 t

It will be understood that various changes may be made in the details ofconstruction and in the arrangement of the parts of the burner controlsystem disclosed herein without departing from the principles of theinvention and the scope of the annexed claims.

Iclaimr t 1. Gas-fired apparatus, comprising: a burner; a gas supplyvalve connected with said burner for controlling the supply of gasthereto; a blower for supplying air under pressure to said burner, ,saidgas supplyvalve including a' seat, and a valve disc cooperable with saidseat to control the flow of gas through said gas supply valve to saidburner, a diaphragm in said gas supply valve on the outlet side of saidvalve disc, a valve stem connecting said diaphragm with said valve disc,and means providing a pressurechamber on the side of said diaphragmremote from said valve disc; a conduit interconnecting said blower-andpressure chamber for conducting air under pressure from said blower tosaid pressure chamber for effecting opening of said gas supply valve, anair 'shut-oflf valve connected in'said conduit for shutting ofi thesupply of air under pressure to said pressurechamber; and bleeder meansestablishing communication between said pressure chamber 1 and theatmosphere for continuously bleeding a portion of the air under pressurefrom said pressure chamber to the atmosphere, whereby upon closing ofsaid air shut-01f valve, the pressure in said pressure chamber will bevented to the atmosphere and the gas supply valve will automaticallyclose.

2. Gas-fired apparatus, comprising: a burner; a gas supply valveconnected with said burner for supplying gas thereto; a blower forsupplying air under pressure to said burner, said gas supply valvehaving an inlet, an outlet, a seat between said inlet and outlet, and avalve disc cooperable with said seat to control the flow of gas throughsaid gas supply valve to said burner; a diaphragm on the outlet side ofsaid valve disc; means operatively connecting said diaphragm with saidvalve disc; means providing a pressure chamber on the side of saiddiaphragm remote from said seat; a normally open air control valvehaving an inlet and an outlet and a seat between said inlet and'outlet,a valve disc engageable with said last-mentioned seat, a stem connectedwith said last-mentioned valve disc, and spring means normallymaintaining said last-mentioned disc out of engagement with its seat; aconduit connecting the inlet of said air valve with said blower; aconduit connecting the outlet of said air valve with said pressurechamber of said gas supply valve to eifect opening of said gas supplyvalve when said blower is in operation; and a thermally responsiveelementtactive on the stem of said air valve to close the sameagainst'said spring pressure to shut oii the air pressure to saidpressure .chamber of said gas supply valve tothereby allow-saidgassupply valve to close. 3. ..Gas-firedf apparatus as defined in claim 2,in which the air control valve includes means compensating forovertravel of the thermally responsive element.

4. Gas-fired apparatus, comprising: a burner; a gas supply ,valveconnected with said burner for supplying gas thereto; a blower forsupplying air under pressure to said burner, said gas supply valvehaving an inlet, an out let, a seat between said inlet and outlet, and avalve disc cooperable with said seat to control the flow of gas throughsaid gas supply valve tosaid burner; a diaphragm on the outlet side ofsaid valve disc; means operatively connecting said diaphragm with saidvalve disc; means providing a pressure chamber on the side of saiddiaphragm remote from said seat; a normally open air control valvehaving an inlet and an outlet and a seat between said inlet and outlet,a valve disc engageable with said last-mentioned 'seat, a stem connectedwith said last-mentioned valve disc, and spring means normallymaintaining said last-mentioned disc out of engagement with its seat; aconduit connecting the inlet of said air valve with said blower; aconduit connecting the outlet of said air valve with said pressurechamber of said gas supply valve to effect opening of said gas supplyvalve when said blower is in operation; a thermally responsive elementactive on the stem of said air valve to close the same against saidspring pressure to' shut 01f the air pressure to said pressure chamberof said gas supply valve to'thereby allow said gas supply valve toclose; and an air shut-01f valve connected in, said last-mentionedconduit for shutting 01f the'supply of air to said pressure chamber toeflect closing of said gas supply valve independently of said thermallyresponsive element. 6 t t References Cited in the file of this patent VUNITED STATES PATENTS 792,087 Thomson June 13, 1905 880,402 ReynoldsFeb. 25, 1908 1,384,247 Fox July 12, 1921 1,539,630 Beaird May 26, 19251,609,891 Smith Dec. 7, 1926 1,645,506 McKee Oct. 11, 1927 1,721,800Wunsch July 23, 1929 1,961,933 Irwin June 5, 1934 2,169,683 Dunham Aug.15, 1939 2,170,342 Bailey Aug. 22, 1939' 2,175,866 Arnold Oct. 10, 19392,321,109 Sellers June 8, 1943 2,396,032 Waterman Mar. 5, 1946 2,405,573Frisch Aug. 13, 1946 2,422,178 Blizard June 17, 1947 Niesmann Jan 22,1952

